Police were present at some polling stations because of fears of fraud

Trials to cut voting fraud worked well at local elections in May but concerns remain about cost and privacy issues, the Electoral Commission has said.

Electronic scanners were used to check voters' signatures in one borough but the process cost more than £10 a time.

There was also a low take-up of a tracking service letting postal voters see if their ballot paper had arrived.

Elsewhere army bases and a supermarket became polling stations. The commission said it would learn from its tests.

Allegations of vote rigging were made in seven of the 32 London boroughs, while police investigated further claims about frauds in Birmingham and Bradford.

Authentication

A total of 21 local authorities in England took part in trials of 16 different methods.

Several of the procedures have already been incorporated in the Electoral Administration Act 2006, which became law last month.

The borough of Newham in east London asked all registered postal voters to authenticate their applications by providing their signature on a separate form.

Almost 12,000 signatures were then checked before counting began, but the relatively high cost of more than £10 per sample was a matter which had raised questions "about value for money", the commission said.

A separate comparison - conducted manually this time - on signatures from about 200 postal voters in Stevenage in Hertfordshire took five hours, a "significant" amount of time.

The tracking service was used by only 8% of postal voters in Shrewsbury and 12% of those submitting papers in advance in the south London borough of Lewisham.

The commission conceded this trial was "relatively expensive" on a "per voter" basis.

It has published evaluations of each of the 16 individual pilot schemes on its website.